We’d had a great run together in office, but Barack had moved on to bigger and better things. He was too big for one country. He was too big for one best friend. He belonged to the world now. I told myself he was happy for him. But if that was really true, why couldn’t I shake the feeling that I’d been dumped the day after graduation?”
-- Joe (Narration) (Part 1, Chapter 3)

Importance: This quote reveals Joe's internal conflict over his friendship with Barack. On the one hand, he recognizes Barack's value and importance to the world: on the other hand, he essentially resents having to share him. He feels abandoned, but at the same time proud of who his friend is and what he has accomplished.

For several decades … I passed through here nearly every day. When the train rounded the bend and sped up on the straightaway, my head was usually...
-- Joe (Narration)  (Part 2, Chapter 8)